1MORE(P) POSIX Programmer's Manual MORE(P)
2
6 more - display files on a page-by-page basis
7
9 more [-ceisu][-n number][-p command][-t tagstring][file ...]
10
12 The more utility shall read files and either write them to the terminal
13 on a page-by-page basis or filter them to standard output. If standard
14 output is not a terminal device, all input files shall be copied to
15 standard output in their entirety, without modification, except as
16 specified for the -s option. If standard output is a terminal device,
17 the files shall be written a number of lines (one screenful) at a time
18 under the control of user commands. See the EXTENDED DESCRIPTION sec‐
19 tion.
20 Certain block-mode terminals do not have all the capabilities necessary
22 to support the complete more definition; they are incapable of accept‐
23 ing commands that are not terminated with a <newline>. Implementations
24 that support such terminals shall provide an operating mode to more in
25 which all commands can be terminated with a <newline> on those termi‐
26 nals. This mode:
27 * Shall be documented in the system documentation
29 * Shall, at invocation, inform the user of the terminal deficiency
31 that requires the <newline> usage and provide instructions on how
32 this warning can be suppressed in future invocations
33 * Shall not be required for implementations supporting only fully
35 capable terminals
36 * Shall not affect commands already requiring <newline>s
38 * Shall not affect users on the capable terminals from using more as
40 described in this volume of IEEE Std 1003.1-2001
41
43 The more utility shall conform to the Base Definitions volume of
44 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
45 The following options shall be supported:
47 -c If a screen is to be written that has no lines in common with
49 the current screen, or more is writing its first screen, more
50 shall not scroll the screen, but instead shall redraw each line
51 of the screen in turn, from the top of the screen to the bottom.
52 In addition, if more is writing its first screen, the screen
53 shall be cleared. This option may be silently ignored on devices
54 with insufficient terminal capabilities.
55 -e By default, more shall exit immediately after writing the last
57 line of the last file in the argument list. If the -e option is
58 specified:
59 1. If there is only a single file in the argument list and that
61 file was completely displayed on a single screen, more shall
62 exit immediately after writing the last line of that file.
63 2. Otherwise, more shall exit only after reaching end-of-file
65 on the last file in the argument list twice without an
66 intervening operation. See the EXTENDED DESCRIPTION section.
67 -i Perform pattern matching in searches without regard to case; see
69 the Base Definitions volume of IEEE Std 1003.1-2001, Section
70 9.2, Regular Expression General Requirements.
71 -n number
73 Specify the number of lines per screenful. The number argument
74 is a positive decimal integer. The -n option shall override any
75 values obtained from any other source.
76 -p command
78 Each time a screen from a new file is displayed or redisplayed
79 (including as a result of more commands; for example, :p), exe‐
80 cute the more command(s) in the command arguments in the order
81 specified, as if entered by the user after the first screen has
82 been displayed. No intermediate results shall be displayed (that
83 is, if the command is a movement to a screen different from the
84 normal first screen, only the screen resulting from the command
85 shall be displayed.) If any of the commands fail for any reason,
86 an informational message to this effect shall be written, and no
87 further commands specified using the -p option shall be executed
88 for this file.
89 -s Behave as if consecutive empty lines were a single empty line.
91 -t tagstring
93 Write the screenful of the file containing the tag named by the
94 tagstring argument. See the ctags utility. The tags feature rep‐
95 resented by -t tagstring and the :t command is optional. It
96 shall be provided on any system that also provides a conforming
97 implementation of ctags; otherwise, the use of -t produces unde‐
98 fined results.
99 The filename resulting from the -t option shall be logically added as a
101 prefix to the list of command line files, as if specified by the user.
102 If the tag named by the tagstring argument is not found, it shall be an
103 error, and more shall take no further action.
104 If the tag specifies a line number, the first line of the display shall
106 contain the beginning of that line. If the tag specifies a pattern, the
107 first line of the display shall contain the beginning of the matching
108 text from the first line of the file that contains that pattern. If the
109 line does not exist in the file or matching text is not found, an
110 informational message to this effect shall be displayed, and more shall
111 display the default screen as if -t had not been specified.
112 If both the -t tagstring and -p command options are given, the -t
114 tagstring shall be processed first; that is, the file and starting line
115 for the display shall be as specified by -t, and then the -p more com‐
116 mand shall be executed. If the line (matching text) specified by the -t
117 command does not exist (is not found), no -p more command shall be exe‐
118 cuted for this file at any time.
119 -u Treat a <backspace> as a printable control character, displayed
121 as an implementation-defined character sequence (see the
122 EXTENDED DESCRIPTION section), suppressing backspacing and the
123 special handling that produces underlined or standout mode text
124 on some terminal types. Also, do not ignore a <carriage-return>
125 at the end of a line.
126
129 The following operand shall be supported:
130 file A pathname of an input file. If no file operands are specified,
132 the standard input shall be used. If a file is '-' , the stan‐
133 dard input shall be read at that point in the sequence.
134
137 The standard input shall be used only if no file operands are speci‐
138 fied, or if a file operand is '-' .
139
141 The input files being examined shall be text files. If standard output
142 is a terminal, standard error shall be used to read commands from the
143 user. If standard output is a terminal, standard error is not readable,
144 and command input is needed, more may attempt to obtain user commands
145 from the controlling terminal (for example, /dev/tty); otherwise, more
146 shall terminate with an error indicating that it was unable to read
147 user commands. If standard output is not a terminal, no error shall
148 result if standard error cannot be opened for reading.
149
151 The following environment variables shall affect the execution of more:
152 COLUMNS
154 Override the system-selected horizontal display line size. See
155 the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8,
156 Environment Variables for valid values and results when it is
157 unset or null.
158 EDITOR Used by the v command to select an editor. See the EXTENDED
160 DESCRIPTION section.
161 LANG Provide a default value for the internationalization variables
163 that are unset or null. (See the Base Definitions volume of
164 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
165 ables for the precedence of internationalization variables used
166 to determine the values of locale categories.)
167 LC_ALL If set to a non-empty string value, override the values of all
169 the other internationalization variables.
170 LC_COLLATE
172 Determine the locale for the behavior of ranges, equivalence
174 classes, and multi-character collating elements within regular
175 expressions.
176 LC_CTYPE
178 Determine the locale for the interpretation of sequences of
179 bytes of text data as characters (for example, single-byte as
180 opposed to multi-byte characters in arguments and input files)
181 and the behavior of character classes within regular expres‐
182 sions.
183 LC_MESSAGES
185 Determine the locale that should be used to affect the format
186 and contents of diagnostic messages written to standard error
187 and informative messages written to standard output.
188 NLSPATH
190 Determine the location of message catalogs for the processing of
191 LC_MESSAGES .
192 LINES Override the system-selected vertical screen size, used as the
194 number of lines in a screenful. See the Base Definitions volume
195 of IEEE Std 1003.1-2001, Chapter 8, Environment Variables for
196 valid values and results when it is unset or null. The -n option
197 shall take precedence over the LINES variable for determining
198 the number of lines in a screenful.
199 MORE Determine a string containing options described in the OPTIONS
201 section preceded with hyphens and <blank>-separated as on the
202 command line. Any command line options shall be processed after
203 those in the MORE variable, as if the command line were:
204 more $MORE options operands
207 The MORE variable shall take precedence over the TERM and LINES vari‐
209 ables for determining the number of lines in a screenful.
210 TERM Determine the name of the terminal type. If this variable is
212 unset or null, an unspecified default terminal type is used.
213
216 Default.
217
219 The standard output shall be used to write the contents of the input
220 files.
221
223 The standard error shall be used for diagnostic messages and user com‐
224 mands (see the INPUT FILES section), and, if standard output is a ter‐
225 minal device, to write a prompting string. The prompting string shall
226 appear on the screen line below the last line of the file displayed in
227 the current screenful. The prompt shall contain the name of the file
228 currently being examined and shall contain an end-of-file indication
229 and the name of the next file, if any, when prompting at the end-of-
230 file. If an error or informational message is displayed, it is unspeci‐
231 fied whether it is contained in the prompt. If it is not contained in
232 the prompt, it shall be displayed and then the user shall be prompted
233 for a continuation character, at which point another message or the
234 user prompt may be displayed. The prompt is otherwise unspecified. It
235 is unspecified whether informational messages are written for other
236 user commands.
237
239 None.
240
242 The following section describes the behavior of more when the standard
243 output is a terminal device. If the standard output is not a terminal
244 device, no options other than -s shall have any effect, and all input
245 files shall be copied to standard output otherwise unmodified, at which
246 time more shall exit without further action.
247 The number of lines available per screen shall be determined by the -n
249 option, if present, or by examining values in the environment (see the
250 ENVIRONMENT VARIABLES section). If neither method yields a number, an
251 unspecified number of lines shall be used.
252 The maximum number of lines written shall be one less than this number,
254 because the screen line after the last line written shall be used to
255 write a user prompt and user input. If the number of lines in the
256 screen is less than two, the results are undefined. It is unspecified
257 whether user input is permitted to be longer than the remainder of the
258 single line where the prompt has been written.
259 The number of columns available per line shall be determined by examin‐
261 ing values in the environment (see the ENVIRONMENT VARIABLES section),
262 with a default value as described in the Base Definitions volume of
263 IEEE Std 1003.1-2001, Chapter 8, Environment Variables.
264 Lines that are longer than the display shall be folded; the length at
266 which folding occurs is unspecified, but should be appropriate for the
267 output device. Folding may occur between glyphs of single characters
268 that take up multiple display columns.
269 When standard output is a terminal and -u is not specified, more shall
271 treat <backspace>s and <carriage-return>s specially:
272 * A character, followed first by a sequence of n <backspace>s (where n
274 is the same as the number of column positions that the character
275 occupies), then by n underscore characters ( '_' ), shall cause that
276 character to be written as underlined text, if the terminal type
277 supports that. The n underscore characters, followed first by n
278 <backspace>s, then any character with n column positions, shall also
279 cause that character to be written as underlined text, if the termi‐
280 nal type supports that.
281 * A sequence of n <backspace>s (where n is the same as the number of
283 column positions that the previous character occupies) that appears
284 between two identical printable characters shall cause the first of
285 those two characters to be written as emboldened text (that is, vis‐
286 ually brighter, standout mode, or inverse-video mode), if the termi‐
287 nal type supports that, and the second to be discarded. Immediately
288 subsequent occurrences of <backspace>/ character pairs for that same
289 character shall also be discarded. (For example, the sequence
290 "a\ba\ba\ba" is interpreted as a single emboldened 'a' .)
291 * The more utility shall logically discard all other <backspace>s from
293 the line as well as the character which precedes them, if any.
294 * A <carriage-return> at the end of a line shall be ignored, rather
296 than being written as a non-printable character, as described in the
297 next paragraph.
298 It is implementation-defined how other non-printable characters are
300 written. Implementations should use the same format that they use for
301 the ex print command; see the OPTIONS section within the ed utility. It
302 is unspecified whether a multi-column character shall be separated if
303 it crosses a display line boundary; it shall not be discarded. The
304 behavior is unspecified if the number of columns on the display is less
305 than the number of columns any single character in the line being dis‐
306 played would occupy.
307 When each new file is displayed (or redisplayed), more shall write the
309 first screen of the file. Once the initial screen has been written,
310 more shall prompt for a user command. If the execution of the user com‐
311 mand results in a screen that has lines in common with the current
312 screen, and the device has sufficient terminal capabilities, more shall
313 scroll the screen; otherwise, it is unspecified whether the screen is
314 scrolled or redrawn.
315 For all files but the last (including standard input if no file was
317 specified, and for the last file as well, if the -e option was not
318 specified), when more has written the last line in the file, more shall
319 prompt for a user command. This prompt shall contain the name of the
320 next file as well as an indication that more has reached end-of-file.
321 If the user command is f, <control>-F, <space>, j, <newline>, d, <con‐
322 trol>-D, or s, more shall display the next file. Otherwise, if display‐
323 ing the last file, more shall exit. Otherwise, more shall execute the
324 user command specified.
325 Several of the commands described in this section display a previous
327 screen from the input stream. In the case that text is being taken from
328 a non-rewindable stream, such as a pipe, it is implementation-defined
329 how much backwards motion is supported. If a command cannot be executed
330 because of a limitation on backwards motion, an error message to this
331 effect shall be displayed, the current screen shall not change, and the
332 user shall be prompted for another command.
333 If a command cannot be performed because there are insufficient lines
335 to display, more shall alert the terminal. If a command cannot be per‐
336 formed because there are insufficient lines to display or a / command
337 fails: if the input is the standard input, the last screen in the file
338 may be displayed; otherwise, the current file and screen shall not
339 change, and the user shall be prompted for another command.
340 The interactive commands in the following sections shall be supported.
342 Some commands can be preceded by a decimal integer, called count in the
343 following descriptions. If not specified with the command, count shall
344 default to 1. In the following descriptions, pattern is a basic regular
345 expression, as described in the Base Definitions volume of
346 IEEE Std 1003.1-2001, Section 9.3, Basic Regular Expressions. The term
347 "examine" is historical usage meaning "open the file for viewing''; for
348 example, more foo would be expressed as examining file foo.
349 In the following descriptions, unless otherwise specified, line is a
351 line in the more display, not a line from the file being examined.
352 In the following descriptions, the current position refers to two
354 things:
355 1. The position of the current line on the screen
357 2. The line number (in the file) of the current line on the screen
359 Usually, the line on the screen corresponding to the current position
361 is the third line on the screen. If this is not possible (there are
362 fewer than three lines to display or this is the first page of the
363 file, or it is the last page of the file), then the current position is
364 either the first or last line on the screen as described later.
365 Help
367 Synopsis:
368 h
371 Write a summary of these commands and other implementation-defined com‐
374 mands. The behavior shall be as if the more utility were executed with
375 the -e option on a file that contained the summary information. The
376 user shall be prompted as described earlier in this section when end-
377 of-file is reached. If the user command is one of those specified to
378 continue to the next file, more shall return to the file and screen
379 state from which the h command was executed.
380 Scroll Forward One Screenful
382 Synopsis:
383 [count]f
386 [count]<control>-F
387 Scroll forward count lines, with a default of one screenful. If count
390 is more than the screen size, only the final screenful shall be writ‐
391 ten.
392 Scroll Backward One Screenful
394 Synopsis:
395 [count]b
398 [count]<control>-B
399 Scroll backward count lines, with a default of one screenful (see the
402 -n option). If count is more than the screen size, only the final
403 screenful shall be written.
404 Scroll Forward One Line
406 Synopsis:
407 [count]<space>
410 [count]j
411 [count]<newline>
412 Scroll forward count lines. The default count for the <space> shall be
415 one screenful; for j and <newline>, one line. The entire count lines
416 shall be written, even if count is more than the screen size.
417 Scroll Backward One Line
419 Synopsis:
420 [count]k
423 Scroll backward count lines. The entire count lines shall be written,
426 even if count is more than the screen size.
427 Scroll Forward One Half Screenful
429 Synopsis:
430 [count]d
433 [count]<control>-D
434 Scroll forward count lines, with a default of one half of the screen
437 size. If count is specified, it shall become the new default for subse‐
438 quent d, <control>-D, and u commands.
439 Skip Forward One Line
441 Synopsis:
442 [count]s
445 Display the screenful beginning with the line count lines after the
448 last line on the current screen. If count would cause the current posi‐
449 tion to be such that less than one screenful would be written, the last
450 screenful in the file shall be written.
451 Scroll Backward One Half Screenful
453 Synopsis:
454 [count]u
457 [count]<control>-U
458 Scroll backward count lines, with a default of one half of the screen
461 size. If count is specified, it shall become the new default for subse‐
462 quent d, <control>-D, u, and <control>-U commands. The entire count
463 lines shall be written, even if count is more than the screen size.
464 Go to Beginning of File
466 Synopsis:
467 [count]g
470 Display the screenful beginning with line count.
473 Go to End-of-File
475 Synopsis:
476 [count]G
479 If count is specified, display the screenful beginning with the line
482 count. Otherwise, display the last screenful of the file.
483 Refresh the Screen
485 Synopsis:
486 r
489 <control>-L
490 Refresh the screen.
493 Discard and Refresh
495 Synopsis:
496 R
499 Refresh the screen, discarding any buffered input. If the current file
502 is non-seekable, buffered input shall not be discarded and the R com‐
503 mand shall be equivalent to the r command.
504 Mark Position
506 Synopsis:
507 mletter
510 Mark the current position with the letter named by letter, where letter
513 represents the name of one of the lowercase letters of the portable
514 character set. When a new file is examined, all marks may be lost.
515 Return to Mark
517 Synopsis:
518 'letter
521 Return to the position that was previously marked with the letter named
524 by letter, making that line the current position.
525 Return to Previous Position
527 Synopsis:
528 ''
531 Return to the position from which the last large movement command was
534 executed (where a "large movement" is defined as any movement of more
535 than a screenful of lines). If no such movements have been made, return
536 to the beginning of the file.
537 Search Forward for Pattern
539 Synopsis:
540 [count]/[!]pattern<newline>
543 Display the screenful beginning with the countth line containing the
546 pattern. The search shall start after the first line currently dis‐
547 played. The null regular expression ( '/' followed by a <newline>)
548 shall repeat the search using the previous regular expression, with a
549 default count. If the character '!' is included, the matching lines
550 shall be those that do not contain the pattern. If no match is found
551 for the pattern, a message to that effect shall be displayed.
552 Search Backward for Pattern
554 Synopsis:
555 [count]?[!]pattern<newline>
558 Display the screenful beginning with the countth previous line contain‐
561 ing the pattern. The search shall start on the last line before the
562 first line currently displayed. The null regular expression ( '?' fol‐
563 lowed by a <newline>) shall repeat the search using the previous regu‐
564 lar expression, with a default count. If the character '!' is included,
565 matching lines shall be those that do not contain the pattern. If no
566 match is found for the pattern, a message to that effect shall be dis‐
567 played.
568 Repeat Search
570 Synopsis:
571 [count]n
574 Repeat the previous search for countth line containing the last pattern
577 (or not containing the last pattern, if the previous search was "/!" or
578 "?!" ).
579 Repeat Search in Reverse
581 Synopsis:
582 [count]N
585 Repeat the search in the opposite direction of the previous search for
588 the countth line containing the last pattern (or not containing the
589 last pattern, if the previous search was "/!" or "?!" ).
590 Examine New File
592 Synopsis:
593 :e [filename]<newline>
596 Examine a new file. If the filename argument is not specified, the cur‐
599 rent file (see the :n and :p commands below) shall be re-examined. The
600 filename shall be subjected to the process of shell word expansions
601 (see Word Expansions ); if more than a single pathname results, the
602 effects are unspecified. If filename is a number sign ( '#' ), the
603 previously examined file shall be re-examined. If filename is not
604 accessible for any reason (including that it is a non-seekable file),
605 an error message to this effect shall be displayed and the current file
606 and screen shall not change.
607 Examine Next File
609 Synopsis:
610 [count]:n
613 Examine the next file. If a number count is specified, the countth next
616 file shall be examined. If filename refers to a non-seekable file, the
617 results are unspecified.
618 Examine Previous File
620 Synopsis:
621 [count]:p
624 Examine the previous file. If a number count is specified, the countth
627 previous file shall be examined. If filename refers to a non-seekable
628 file, the results are unspecified.
629 Go to Tag
631 Synopsis:
632 :t tagstring<newline>
635 If the file containing the tag named by the tagstring argument is not
638 the current file, examine the file, as if the :e command was executed
639 with that file as the argument. Otherwise, or in addition, display the
640 screenful beginning with the tag, as described for the -t option (see
641 the OPTIONS section). If the ctags utility is not supported by the
642 system, the use of :t produces undefined results.
643 Invoke Editor
645 Synopsis:
646 v
649 Invoke an editor to edit the current file being examined. If standard
652 input is being examined, the results are unspecified. The name of the
653 editor shall be taken from the environment variable EDITOR , or shall
654 default to vi. If the last pathname component in EDITOR is either vi or
655 ex, the editor shall be invoked with a -c linenumber command line argu‐
656 ment, where linenumber is the line number of the file line containing
657 the display line currently displayed as the first line of the screen.
658 It is implementation-defined whether line-setting options are passed to
659 editors other than vi and ex.
660 When the editor exits, more shall resume with the same file and screen
662 as when the editor was invoked.
663 Display Position
665 Synopsis:
666 =
669 <control>-G
670 Write a message for which the information references the first byte of
673 the line after the last line of the file on the screen. This message
674 shall include the name of the file currently being examined, its number
675 relative to the total number of files there are to examine, the line
676 number in the file, the byte number and the total bytes in the file,
677 and what percentage of the file precedes the current position. If more
678 is reading from standard input, or the file is shorter than a single
679 screen, the line number, the byte number, the total bytes, and the per‐
680 centage need not be written.
681 Quit
683 Synopsis:
684 q
687 :q
688 ZZ
689 Exit more.
692
694 The following exit values shall be returned:
695 0 Successful completion.
697 >0 An error occurred.
699
702 If an error is encountered accessing a file when using the :n command,
703 more shall attempt to examine the next file in the argument list, but
704 the final exit status shall be affected. If an error is encountered
705 accessing a file via the :p command, more shall attempt to examine the
706 previous file in the argument list, but the final exit status shall be
707 affected. If an error is encountered accessing a file via the :e com‐
708 mand, more shall remain in the current file and the final exit status
709 shall not be affected.
710 The following sections are informative.
712
714 When the standard output is not a terminal, only the -s filter-modifi‐
715 cation option is effective. This is based on historical practice. For
716 example, a typical implementation of man pipes its output through more
717 -s to squeeze excess white space for terminal users. When man is piped
718 to lp, however, it is undesirable for this squeezing to happen.
719
721 The -p allows arbitrary commands to be executed at the start of each
722 file. Examples are:
723 more -p G file1 file2
725 Examine each file starting with its last screenful.
727 more -p 100 file1 file2
729 Examine each file starting with line 100 in the current position
731 (usually the third line, so line 98 would be the first line
732 written).
733 more -p /100 file1 file2
735 Examine each file starting with the first line containing the
737 string "100" in the current position
738
741 The more utility, available in BSD and BSD-derived systems, was chosen
742 as the prototype for the POSIX file display program since it is more
743 widely available than either the public-domain program less or than pg,
744 a pager provided in System V. The 4.4 BSD more is the model for the
745 features selected; it is almost fully upwards-compatible from the 4.3
746 BSD version in wide use and has become more amenable for vi users.
747 Several features originally derived from various file editors, found in
748 both less and pg, have been added to this volume of
749 IEEE Std 1003.1-2001 as they have proved extremely popular with users.
750 There are inconsistencies between more and vi that result from histori‐
752 cal practice. For example, the single-character commands h, f, b, and
753 <space> are screen movers in more, but cursor movers in vi. These
754 inconsistencies were maintained because the cursor movements are not
755 applicable to more and the powerful functionality achieved without the
756 use of the control key justifies the differences.
757 The tags interface has been included in a program that is not a text
759 editor because it promotes another degree of consistent operation with
760 vi. It is conceivable that the paging environment of more would be
761 superior for browsing source code files in some circumstances.
762 The operating mode referred to for block-mode terminals effectively
764 adds a <newline> to each Synopsis line that currently has none. So, for
765 example, d <newline> would page one screenful. The mode could be trig‐
766 gered by a command line option, environment variable, or some other
767 method. The details are not imposed by this volume of
768 IEEE Std 1003.1-2001 because there are so few systems known to support
769 such terminals. Nevertheless, it was considered that all systems should
770 be able to support more given the exception cited for this small commu‐
771 nity of terminals because, in comparison to vi, the cursor movements
772 are few and the command set relatively amenable to the optional <new‐
773 line>s.
774 Some versions of more provide a shell escaping mechanism similar to the
776 ex ! command. The standard developers did not consider that this was
777 necessary in a paginator, particularly given the wide acceptance of
778 multiple window terminals and job control features. (They chose to
779 retain such features in the editors and mailx because the shell inter‐
780 action also gives an opportunity to modify the editing buffer, which is
781 not applicable to more.)
782 The -p (position) option replaces the + command because of the Utility
784 Syntax Guidelines. In early proposals, it took a pattern argument, but
785 historical less provided the more general facility of a command. It
786 would have been desirable to use the same -c as ex and vi, but the let‐
787 ter was already in use.
788 The text stating "from a non-rewindable stream ... implementations may
790 limit the amount of backwards motion supported" would allow an imple‐
791 mentation that permitted no backwards motion beyond text already on the
792 screen. It was not possible to require a minimum amount of backwards
793 motion that would be effective for all conceivable device types. The
794 implementation should allow the user to back up as far as possible,
795 within device and reasonable memory allocation constraints.
796 Historically, non-printable characters were displayed using the ARPA
798 standard mappings, which are as follows:
799 1. Printable characters are left alone.
801 2. Control characters less than \177 are represented as followed by
803 the character offset from the '@' character in the ASCII map; for
804 example, \007 is represented as 'G' .
805 3. \177 is represented as followed by '?' .
807 The display of characters having their eighth bit set was less stan‐
809 dard. Existing implementations use hex (0x00), octal (\000), and a
810 meta-bit display. (The latter displayed characters with their eighth
811 bit set as the two characters "M-" , followed by the seven-bit display
812 as described previously.) The latter probably has the best claim to
813 historical practice because it was used with the -v option of 4 BSD and
814 4 BSD-derived versions of the cat utility since 1980.
815 No specific display format is required by IEEE Std 1003.1-2001. Imple‐
817 mentations are encouraged to conform to historic practice in the
818 absence of any strong reason to diverge.
819
821 None.
822
824 Shell Command Language , ctags , ed , ex , vi
825
827 Portions of this text are reprinted and reproduced in electronic form
828 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
829 -- Portable Operating System Interface (POSIX), The Open Group Base
830 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
831 Electrical and Electronics Engineers, Inc and The Open Group. In the
832 event of any discrepancy between this version and the original IEEE and
833 The Open Group Standard, the original IEEE and The Open Group Standard
834 is the referee document. The original Standard can be obtained online
835 at http://www.opengroup.org/unix/online.html .
836IEEE/The Open Group 2003 MORE(P)